fix(desktop): time out ICE gathering

internal/desktop/webrtc.go

@@ -16,6 +16,7 @@ import (
 const (
 	desktopReliableInputChannelLabel = "input"
 	desktopMoveInputChannelLabel     = "input-move"
+	desktopICEGatheringTimeout       = 10 * time.Second
 )
 
 type WebRTCServer struct {
@@ -230,7 +231,9 @@ func (w *WebRTCServer) ProcessOffer(sdpOffer string) (string, error) {
 		return "", fmt.Errorf("failed to set local description: %w", err)
 	}
 
-	<-gatherComplete
+	if err := waitForICEGatheringComplete(gatherComplete, desktopICEGatheringTimeout); err != nil {
+		return "", err
+	}
 
 	localDesc := pc.LocalDescription()
 	if localDesc == nil {
@@ -240,6 +243,15 @@ func (w *WebRTCServer) ProcessOffer(sdpOffer string) (string, error) {
 	return localDesc.SDP, nil
 }
 
+func waitForICEGatheringComplete(done <-chan struct{}, timeout time.Duration) error {
+	select {
+	case <-done:
+		return nil
+	case <-time.After(timeout):
+		return fmt.Errorf("timed out waiting for ICE gathering after %s", timeout)
+	}
+}
+
 // AddICECandidate adds a remote ICE candidate
 func (w *WebRTCServer) AddICECandidate(candidate webrtc.ICECandidateInit) error {
 	w.mu.Lock()

internal/desktop/webrtc_test.go

@@ -1,6 +1,9 @@
 package desktop
 
-import "testing"
+import (
+	"testing"
+	"time"
+)
 
 func TestIsDesktopInputDataChannelLabelAllowsReliableAndMoveChannels(t *testing.T) {
 	if !isDesktopInputDataChannelLabel(desktopReliableInputChannelLabel) {
@@ -13,3 +16,25 @@ func TestIsDesktopInputDataChannelLabelAllowsReliableAndMoveChannels(t *testing.
 		t.Fatalf("expected unrelated data channel label to be ignored")
 	}
 }
+
+func TestWaitForICEGatheringCompleteReturnsWhenDoneCloses(t *testing.T) {
+	done := make(chan struct{})
+	close(done)
+
+	if err := waitForICEGatheringComplete(done, time.Second); err != nil {
+		t.Fatalf("expected closed gathering channel to succeed: %v", err)
+	}
+}
+
+func TestWaitForICEGatheringCompleteTimesOut(t *testing.T) {
+	done := make(chan struct{})
+
+	start := time.Now()
+	err := waitForICEGatheringComplete(done, 10*time.Millisecond)
+	if err == nil {
+		t.Fatalf("expected timeout error")
+	}
+	if elapsed := time.Since(start); elapsed > time.Second {
+		t.Fatalf("timeout helper waited too long: %s", elapsed)
+	}
+}